package 刷题;

import java.text.DecimalFormat;
import java.util.Scanner;

public class 圆的面积 {
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        double PI=3.14159;
        double r=scanner.nextDouble();
        double s=r*r*PI;
        DecimalFormat df=new DecimalFormat("0.000");
        System.out.println(df.format(s));
    }
}
